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Symfony UX & Chart.js

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We now know Stimulus pretty well, which is really just a nice JavaScript library that has nothing to do with Symfony. So then... what exactly is Symfony UX?

To answer that, go to At its most basic, Symfony UX is a growing list of pre-built Stimulus controllers that you can install to get free functionality. For example, one of them is a controller that integrates Chart.js: a completely independent, lovely JavaScript-powered chart library.

This is perfect... because our sales are really starting to take off. People love our junk, uh, minimalist products! So let's install and use this UX package to build a sales graph on an admin page. I've already created that page at "/admin"... but it's not very interesting yet... and none of these links go anywhere.

Installing symfony/ux-chartjs

Ok: let's check out the docs for Symfony UX chartjs. Scroll down... Whoa. Stimulus and Chart.js are both pure JavaScript libraries. So it's a little interesting that the first step is to install a PHP package. Why are we doing that? Let's find out! Copy the composer require line and head over to your terminal.

I committed all my changes before hitting record so I can easily see any changes that the Flex recipe for this package might make. Paste and go:

composer require symfony/ux-chartjs:1.2.0

While this loads, your Encore build may start failing: don't worry about that for now. When it finishes, run:

git status

Interesting! This modified composer.json and composer.lock, which is totally normal. And the PHP package we just installed is actually a Symfony bundle, so its Flex recipe auto-enabled that bundle in config/bundles.php and updated the symfony.lock file.

UX PHP Packages Come with a JavaScript Package

But here's where things get interesting, really interesting. The recipe also updated our package.json file as well as some other file called assets/controllers.json.

Let's see what changed in package.json:

git diff package.json

Woh! It added a new package! But instead of a version number on the right, it's pointing to a directory inside of vendor/. Let's go check out that path. It was vendor/symfony/ux-chartjs/ then Resources/assets. Cool! This directory is a JavaScript package! How can I tell? It has a package.json file like all JavaScript libraries and, in the src/ directory, a Stimulus controller!

Well, in reality, when we use this package, the compiled controller in the dist/ directory is what will truly be used... but reading the one in src/ is easier.

So: what does this mean for us? It means that each Symfony UX library - like ux-chartjs - is actually two things: a PHP bundle and a JavaScript package. There is also some magic related to how this controller is registered in our app... but we'll talk about that in a few minutes.

Anyways, we have a new Symfony bundle in our vendor/ directory and a new JavaScript package registered in package.json - let me open that - which points to a directory in that bundle.

yarn install --force to Put the Package in node_modules/

Ok, back to the docs! The next step is to run yarn install --force. Copy that.

Normally, if you add a package to package.json, you need to run yarn install to actually download that into the node_modules/ directory. And actually, that's exactly what just happened to us! The Flex recipe added a new package to our package.json file.

Move over to the terminal that's running Encore, hit Ctrl+C to quit, then paste this command:

yarn install --force

This command forces yarn to reinstall our dependencies. The important part is that it copies the directory from the bundle into node_modules/ so that it looks and acts like any normal package.

Let's go find that: let me close a couple of things, then open node_modules/, and @symfony/. Cool! We of course have a webpack-encore/ directory but we also have a package called ux-chartjs.

Let's go re-build our assets:

yarn watch

Using the new Stimulus Controller

Ok: so how do we use the new Stimulus controller that lives in the package?

To answer that... let's keep following the docs! Scroll down. To build the JavaScript-powered chart, we're... woh! We're going to write PHP code!

Copy the top half of this code then head over and open up our admin controller, which is src/Controller/AdminController.php. Paste that code on top. And... let's see, we also need this ChartBuilderInterface argument. Add ChartBuilderInterface $chartBuilder. And... we need a use statement for this Chart class. I'll delete the "t", re-type, and hit tab to get it on top.

35 lines | src/Controller/AdminController.php
// ... lines 1 - 6
use Symfony\UX\Chartjs\Builder\ChartBuilderInterface;
use Symfony\UX\Chartjs\Model\Chart;
// ... line 9
class AdminController extends AbstractController
// ... lines 12 - 14
public function dashboard(ChartBuilderInterface $chartBuilder)
$chart = $chartBuilder->createChart(Chart::TYPE_LINE);
'labels' => ['January', 'February', 'March', 'April', 'May', 'June', 'July'],
'datasets' => [
'label' => 'Sales!',
'backgroundColor' => 'rgb(255, 99, 132)',
'borderColor' => 'rgb(255, 99, 132)',
'data' => [522, 1500, 2250, 2197, 2345, 3122, 3099],
// ... lines 29 - 32

But wait: where did these classes come from? Remember: we did just install a new bundle... and bundles give us new classes and services. Autowiring ChartBuilderInterface will give us a new service that's really good at building chart data in PHP. Pass the $chart variable into the template: chart set to $chart.

35 lines | src/Controller/AdminController.php
// ... lines 1 - 14
public function dashboard(ChartBuilderInterface $chartBuilder)
// ... lines 17 - 29
return $this->render('admin/dashboard.html.twig', [
'chart' => $chart
// ... lines 34 - 35

Okay. How do we render the chart? Go back to the docs and scroll down one more time. Ah ha! The bundle also gave us a new Twig helper. Copy that and go find the template for this page: templates/admin/dashboard.html.twig.

Then... all the way at the bottom, paste.

110 lines | templates/admin/dashboard.html.twig
// ... lines 1 - 2
{% block body %}
<div class="container-fluid">
<div class="row">
// ... lines 6 - 101
<div class="col-10 mt-4">
<h1>Admin Dashboard</h1>
{{ render_chart(chart) }}
{% endblock %}

This uses the new function render_chart() from the bundle to render our chart variable.

I... guess we're done? Head back to our site and refresh the admin page. Whoa! We are done! We have a JavaScript-powered graph! That's extra amazing since all we did was composer require a PHP package, run yarn install, then write some PHP code!

That is the power of Symfony UX.

But... how exactly does this all work and connect together? What does render_chart() actually do? How is that Stimulus controller from the bundle being used? When will I find my car keys?

Let's answer... most of these questions, next.